Vacuum-pump



Sheets-Sheet 1.' E. D. GHAPLIN. VACUUM PUMP.

(No Model.)

No. 521,432. Patented June 12, 1894.

In I l w 'lwss es.

(No Model.) 4 sheetssh eet 3.

E. D. 'GHAPLIN. VACUUM PUMP.

N0. 521,432v Patented June 12,1894.

Zokbneases- 1511/? zawm' 1 d iii/trad 3. 24%.

(No Model.) ,4 Sheets-Sheet 4.

E. D. OHAPLIN.

VACUUM PUMP.

No. 521,432. Patented June 12,1894.

12, I ive/8766:011-

@ZMWA g I UNITED STATES.

PATENT OFFICE.

EDWIN D. OHAPLIYN, or NATIOK, MASSACHUSETTS.

VACUUM-PUMP.

SPECIFICATION forming'part or Letters Patent No. 521,432, dated June 12, 1894.- Application filed May 29, 1893. Serial No. 475,855. (No model) To all whom it may concern.-

Be it known thatI, EDWIN D. CHAPLIN, of

- Natick, county of Middlesex, State of Massachusetts, have invented an Improvement-in Vacuum-Pumps,of which the following description, in connection withthe accompanying drawings, is a specification, like letters on the drawings 'repre'sentinglik'e parts.

This invention relates-to vacuum pumps, ithavingespecialreference to pumps e1nployed to exhaust the air from incandescent lamp bulbs. As the air contained in lamp bulbs always carries a certain quantity of moisture, and as it is'difficult to obtain a high vacuum in the presenceof moisture, it is the common practice to first exhaust thegreater part, sayninety-five per cent, of the air together with a like percentage of themoisture,

by a vacuum pump of'ordinary construction, and then exhaust the balanceof the air, or as much of the same as is possible, by a second specially constructed pump, Which, by

reason, of its special construction, together with the absence of any appreciable quantity of moisture enables a'high vacuum to be obtained. Pumps for this second or final eat- I hausting, as heretofore constructed have usually been provided with an airinlet controlled by a valve which it is necessary to cover or flood with a liquid, usually oil, in order to form a liquid seal about the valve to'prevent -p0ssible leakagehln practical operation,

however, it has been found that as the air valve is opened, the sealingliq'uid has a tendency to cling to and follow the valve like the stretching of a piece ofrubber and form a thin film of liquid stretching from and surrounding the valve seat 'to the open valve, which film therar'efied air in the bulbs has not sufficient pressure to break, this film being so strong that in a high vacuum'it absolutely prevents the entrance or expansion of air from the bulbs into the pump cylinderf To obviate this difficulty pumps have been constructed having the air inlet in thejside of the pump cylinder, so as to be opened and closed by thepiston as it reciprocates in said cylinder, the piston fulfilling the functions of a valve. In pumps of thislatter construction, that is, having the; side air inlet, the tight fitting piston which excludes any c0norder that said piston in its return or expelling stroke might first close or cover the inlet, and thereafter expel the air from the cylinder. If such side inlet were located near the bottom of the cylinder, the air which has entered and filled the cylinder during the drawing-in stroke of the piston would simply'be returned back again through the open inlet into the bulbs from which it hasexpanded, before the moving piston could reach and cover the inlet toprevent such return. It has also been the middle of the cylinder, or near the end of its drawing-in stroke as described,'the. rarefied air has not sufficient time between the uncovering of the inlet as the piston reaches the-end of its stroke and the closing of the inlet by the return movement of the piston,

to expand into and fill the cylindenfor rare found that whenthe air inlet is placednear fied air is sluggish in its'mo'vements and does not readily expand to fill the cylinder, but needs to be drawn or sucked into the cylinder, by almoving piston, which cannot be done when the inlet is "not uncovered until the piston has practically reached the end of such drawing-in orsu'cking stroke.

In my efforts to perfect vacuum pumps I I have aimed to construct a pump, first, which should have the air inlet in the side of the.

pump cylinder to avoid the oil or liquid film surrounding the open valve, referredto; sec ond, tojplacethe said air inlet near or at the bottom of the cylinder or near the beginning of the drawing-in stroke of the piston, in order that said inlet should be uncovered at the very beginning of the stroke to therebygivej the longest possible time during the stroke .of the piston in which the air might expand into and fill the cylinder, and 'thereby'also .avail myself of the full drawing-in or sucking movement of the piston to draw or suck the rarefied air into the cylinder; and lastly to provide a means for closing the'said air inlet quickly at the end of the drawing-inc stroke of thepistominorder that none of the air drawn or expanded into the cylinder be-.

hind the piston shall be returned or forced back again into the bulbs before the piston in its return or expelling stroke should reach and cover the said inlet to prevent such return.

The result of my efforts is the invention forming the subject matter of this present 7 application, and in which the principal or distinctive feature is the employment of two pistons within the pump cylinder, one piston moving within the other, which latter moves to open and close the air inlet and at the same time constitutes a cylinder in which the other piston which draws in and expels the air is reciprocated. These pistons which are preferably provided with valves as necessary may be reciprocated relatively to each other in any suitable or desired manner, but I prefer toemploy as a motive power oil or other liquid under pressure, I having found that by the use of hydraulic pressure, I can, as I believe, better control the movements of the piston to facilitate the exhaustion of the air.

The invention also comprehends various constructional features and details which will be fully hereinafter described and pointed out in the claims.

Figure 1 of the drawings represents in side elevation partially broken away one form of pump embodying this invention; Fig. 2, a vertical section of the same taken on the dotted line 50-00; Fig. 3, a vertical section taken on the dotted line .r'-:n', Fig. 2; Fig. 4, a top or plan view of Fig. 1 partially broken away; Fig. 5, an enlarged face view of one pair of power cylinders Fig. 1, with the valve chest caps removed to expose the valves; Fig. 6, a vertical section taken on the dotted line 'yy, Fig.5; Fig. 7, a horizontal section of one of the valves, with its valve seat, the section being taken on the dotted line y'-y', Fig. 5; Fig. 8,. a cross section taken on the dotted line gfi-gfi, Fig. 6; Fig. 9, a section of one of the valves taken on the dotted line Z-z, Fig. 5; Fig. 10, adetail showing the form of pipes which I prefer to use. Fig. 11 shows the valve h, split and opened like a clam shell to show both sides in perspective. Fig. 12 shows its valve seat; Fig. 13, a view of the valve h, similar to the view Fig. 11, and Fig. 14, its valve seat.

Referring to the drawings which illustrate one form or embodiment of my invention, A represents a suitable base, upon which are erected two vertical pumps, and as both are of the same construction, a detailed description of one only is suliicient, it being 1rnderstood that like letters represent like parts in both pumps.

B represents the vertical pump cylinder, the lower cylinder head I) of which is made conical, as shown in Fig. 2, while the upper cylinder head I) isprovided at its inner side or face with an annular cone-shaped recess Z1 said upper cyliuderhead being provided with a vertically extended annular flange b upon of the piston 0. its under side with one or more upwardly opening valves f its upper side being per-- which is sustained and bolted the cylinder head a of the power cylinder 0, the latter in turn at its upper end supporting and having secured to it a second vertical power cylinder 0' provided with the proper cylinder heads 0 lb. Within the cylinder B I have provided,

in accordance with this invention, two independent pistons or plungers e andf, the piston e as shown being made cup-shaped and long, and provided at its sides with suitable packing rings a. The annular cone-shaped top of this outer piston e is fitted to enter the annular recess b in the top cylinder-head b. The top and sides of the piston e are herein shown as formed of independent parts bolted together, but itis evidentthe entire piston may be formed in a single piece or member if desired. Within thiscup-shaped piston c, which in effect constitutes asecond moving cylinder, is placed the inner piston fishorter in length than the outer piston cand preferably box-like in construction, its under side having prefer- :tably a conicalrecess to correspond with the conical cylinder head I) with which it contacts whenat the lower end of the stroke, the upper cone-shaped facef' of the said pistonf being formed to enter and fit a corresponding recess e at the end or inner face of the head The pistonf is provided at forated by ports or openings f", said piston in practice being preferably completely filled with oil or other liquid. The piston e is provided at its head with outwardly openingvalves 6 while the top cylinder head I) is provided with upwardly opening valves la.

The piston c is shown as fast on the lower der-head c of the power cylinder 0 into the latter where it is provided with a piston f The power cylinder 0 is provided atone side with a suitable valve seat cflshown separately 1 in Fig. 12, and as circular, to which lead the ports 0, c, from the upper and lower ends respectively of the power cylinder 0, the port a entering the valve seat at one side thecenter of the latter, while the port 0 enters the valve seat below the center substantially ninety degrees distant from the port a". The

f power cylinder 0' is also provided with a circular valve seat c, see Fig. 14, to which lead the ports 0 0 see dotted lines Fig. 5, from 0 leading to one side of their'respective valve seats, as shown in Figs. 5, 12 and 14.

The valves h and h, which I have herein shown and prefer to employ, are in the form of disks provided at their peripheries with intermeshing teeth whereby rotation of either valve causes a like but opposite rotation of its mating valve.

Referring particularly to Fig. 2, the valve h is mounted upon a central or axial shaft h journaled in a suitable boss h formed on a valve face plate h bolted to the cylinder casting, said shaft'having at its outer end keyed or otherwise secured to it a worm wheel h,

, which, see'Fig. 1, is in mesh with and rotated by a worm h on a horizontally arranged shaft h journaled in suitable bearings h", formed in or secured to the frame of the pump, and provided with a belt pulley h by means of which the said worm shaft may be belted to and driven by a suitable driving shaft or wheel, or if desired such worm shaft may be rotated by other means than that herein 1 shown. The valve h is herein shown as jour naled loosely upon a pin or short shaft h? mounted in the cylinder casing Of'and in the face-plate h secured thereto. The power fluid, preferably a liquid, as oil under pressure, is conducted to the valve h through a pipe entering the'face-plate'h at the point h see dotted lines Fig. 1, while the said power fluid for the valve h enters the said faceplate at h, see Figs. 1 and 2. From the power inlet h for the upper valve h, branches h lead to'diametrically opposite points directly over the entrances to the ports 0 c of the cylinder- O. The valve his provided at its outer face side, see Figs. 5, 7 and 11, with an arc-shaped depression. 71 in the middle of which is located a port h which extends through to the inner face side of the valve; The valve h is also provided at its rear side with an arc-like exhaust depression h The valve h is provided with the long arc-shaped port h extending through the valve, while the said valve at its rear side is provided with an arc-like exhaust'de'pression h".

Referring now to Fig.1, the shaft h has fast upon it the bevel wheel'iin mesh with a bevel wheel 1; fast on the upper end of the vertical shaft i journaled in suitable bearings 2' in theframe, said shaft constituting the driving shaft of any suitable or usual rotary or centrifugal pump I, supported upon the base A, said pump'having two outletpipes 01 leading to the two pumps respectively, each of its delivery pipes 11 being divided at its end, one branch '6 leading tothe inlet h for the valve h, while the branch i leads to the .the power cylinders C and O inlet h for the valve h. the valve h enters a pipe 2' Fig. 1, while the exhaust from the valve h enters a pipe i said pipes joining a single pipe 71 which leads to and constitutes one -of the suction pipes for the'pump I, said pump .I-having'another like suction pipe leading to the other vacuum pump, as will be clearly understood byreference to Fig. 1.

M represents the air pipe which connects the air inlet of the pump cylinder with the bulbs or other devices which are tobe exhausted, said pipe M in the present instance comprising two concentric tubes or pipe m,

m, the inner pipe m constituting the air conduit proper, the space between it. and the The exhaust from outer pipe being preferably filled with oil or other sealing fluid to prevent possible leakage.

When the shaft h is rotated, the pump I maintains a constant pressurp of fluid in its delivery pipes 2' and the operation of the pump may then be described as follows, viz: -The valves h and h are rotated by the shaft h in the direction of the arrows Fig. 5. As soon as the valves have been rotated a short distance from-their position Fig. 5, the inlet port h of the valve h, and the inlet port h of the valve h will be moved gradually into position over the ports 0 and c of and leading to the lower ends respectively of admitting fluid underpressure from the supply pipe i to the said cylinders below the pistons e and f therein, causingthe latter to risetogether and thereby move the pump pistons e and f, in the pump cylinder B in unison, the said pistons as herein shown at the very beginning of their movement uncovering the air inlet d. The outer' piston e has a shorter stroke than the inner piston f and reaches the end of its stroke in contact with the top cylinder head h before the piston f has completed more than half its movement, the latter piston'f continuing its movement thereafter toward the head of the piston e. The continuous rotation of the valves at this point brings the inlet-port h of the valveh into position over and communicating with theport 0 leading to the upper end of the lower cylinder 0, the exhaust port h of said valve at the same time reaching a position over and in communication with the port leading to the lower end of the'cylinder, with the result that the direction of movement of piston begins its return or downward movement toward the still rising pistons meeting and contacting with each other just before the piston 6 reaches the end of its downward movement, at which time the valve h in its rotation has carried its inlet port h into the piston e is-quickly changed, and the said I pistonf, the two position over the port 0 leading to the upper end of the upper cylinder 0' and its exhaust port h 'over the port 0 of said cylinder to change the direction of movement of the piston f in the pump cylinder,:and cause the latterto descend to the bottom of the pump cylinder preferably in unison and in contact with the piston c throughlthebalance of the stroke of the latter, the piston f thereafter moviugdownwardly independently of andwithin the .piston e to the end of itsstroke. The movements of the pistons are preferably timed as described, but it is evident they may be timed differently or their relative movements changed without departing from the-scope of the in vention. Thesmeehanical operation of the pump hav- 1 ing now been described, the mannerin which theair is exhausted from the bulbs will be described.

Referring to Fig.'2, both pistons are shown at the endsof their downstrokesin contact with the bottom cylinder-head b. As previously 1desc'ribed,'both pistons begin their upward movements or strokes together, and" at theverybeginning of theirstrokes uncover l the air'inlet (l, sothat the retreatingpistonsf actto draw or suck the'air from the lamp bulbs throughthepipe M into thecylinder to 'fill the space left 'by the retreating pistons. i The outer, and what Itermjthecut-0if pistonc having a shorterstroke reaches theend of its stroke considerablyin-advance of "-the' main piston f, and immediately begins its re 11 turn or downward stroke before the piston f; has finished its up-stroke, the two pistons meeting,as described, just before the cut-elf pistone has reached the end of itsreturn or downwardstrokaor just as it'has passed and closed the air inlet to cut-cit the cylinderf from the lamp bulbs. The two pistons now' descendtogether through the balance of-and until the cut-ofi piston e'has reached the endiof itsstroke when the said cut-ofi piston stops and dwellsuntiltheinuer ormain pistonfinishes its downward stroke and contacts with the bottom cylinder-head b, such downward movement of the-main pistonfcausing the air previouslydrawn into the cylinder byits up-stroke, to be forced upwardly through and 1 opening thevalvef into the oilor liquid containedwitliin'the piston, the air'rising through i the latter andthroughthe ports f into thej auxiliary cylinder formed withiuthe-cut-ofl? piston c-and between it and thesaid piston f. j, Atthe next up-stroke of these two pistons this ibody-0f rarefied air-is carried bodily upward between the two pistonsuntil the outerj or cut-olfp'iston reaches the end of its stroke, when furtherrising movement of the piston? f within the cut-off'piston, together with the? return or downward movement of the said; cut-off piston, causes the rarefied air -con-; tained between the two to be compressed un til the two pistons meet, when the piston f,j strikingthe valves a will open the latter and cause the air compressed between the two, pistonsto be expelled through the saidvalves into thespace between the cut-ofipiston e. andthe cylinder head l) in whichit is compressed at the.next-upwardstrokeof the cutoif piston, and expelled from the cylinder B when the said cut-oif piston reaches the end of its stroke and contacts with and opens the valves b the air thus expelled escaping into the atmospherethrough theexhaust N, Fig.3.

The advantages of this pump-areas ,follows, viz:-The air .inlet dbeingplaced at or near the bottom .of the pump cylinder, is substantially at the very'beginning of the strokeuncovered or openedlto permittheair 1 from the bulbs to be sucked or drawn into the cylinder by the upward or drawing-in movements of the pistons, said inlet remaining open until the inner main piston f has nearly or quite reached the end of its upward stroke, so that the benefit of its full strokeiis obtained in drawing in the air from thelbu'lb. The cut-off piston begins to cut-off or close the air inlet before the main piston reaches the end of its up or drawing-in stroke, sothat :bythe time the said inner or main piston begins its down or expelling stroke, the said cut-elf piston may completely close the air inlet, andthereby prevent the return of any air from the-cylinders to the bulbs, so that all :the air previously drawn intothecylindermust of necessity be expelled through the valve f rather than returned back to the bulbs. I am thus enabled to open and close the air inlet at suchtimes as will securethemost efl'ective exhaustion of air from the lamp bulbs,and this without using the ordinary valves, but by usingthe cut-01f piston e, which, as hereinbeforestated, is not open to the objection of the oil film closingthe inlet. The .air is notrequired toexpand into and of itselrnll the cylinder,but is,from substantially the the pistons e and f, I am enabledto better controland govern the movements of said pistons and to give either or both of them such proper amount of dwell at the ends of their respective strokes as .Will most increase the eiiiciency of the pump.

By referenceto Fig. 2'it will be seenthat two degrees of vacuum are formed at each stroke into which the rarefied air drawn from the lamp bulbsis exhausted for example, "the airdrawn from thebulbsinto the l cylinder beneath the piston f isfirst expelled wlOO or forced into the vacuum chamber within the two pistons, and from such vacuum chamber is again expelled orlforced into a second vacuum chamber between the piston e .and the top'cylinder-head bf, the great advantage of thisbeing that the rarefied air from the lamp bulbs and which is drawn into the cyl- 1nder by the piston f, is more easily forced or expanded successively into the vacuum chamber between the two pistons, and between the piston e and the cylinder head I), and then into the atmosphere, than could be possible were it attempted to expel such rarefied air from the cylinder B direct into the atmospheric pressure without the intervent1on of the vacuum chambers.

The pump I, which constitutes a pressure creating device to store pressure with which to actuate the power pistons, is shown connected with the same mechanism which actuates the valves, so that when once properly ad usted the rapidity with which the pressure is created or stored Varies directly wlth the movements of the valves, and the consequent rapidity with which the pressure is utilized. It will also be seen that a series of pumps may be connected together, so that all the valves may be moved constantly with relat on to each other, and a single pressure creating device employed for or be provided the several pistons within a single cylinder, as shown.

A single pump cylinder, or with its connected power cylinders, which constitutes what I herein term a single pump," fulfills the functions, viz:provides different degrees of vacuum, usually fulfilled by two or more independent pumpsconnected together,

so thata complete exhaust apparatus is in my nvention embodied in a single pump, whereas 1n the present construction a plurality of independent pumps must be connected together to secure different degrees of vacuum.

In practice both pumps are connected as shown n Fig. 1, so that they'operate together 1n expanding air from the lamp bulbs.

I have herein shown and described my in vention as embodied in one form of apparatus or' machine, but this invention is not limited to the particular construction or form of pump shown, for it is evident the gist of the invention may be embodied in many varying constructions without departing from the spirit and scope of the invention.

I have herein employed the terms upper and lower in connection with the power cylinders and have described the apparatus as vertically arranged, but it will be obvious that my invention would not be departed from by laying the apparatus on its side.

In vacuum pumps which i are designed for use in creating the highest possible vacuum it is absolutely necessary that the piston or pistons moving within the pump cylinder be firmly and squarely seated at each end of their respective strokes, in order that all air contained between the moving piston and the wall which constitutes the end of the cylinder within which the piston moves, may be expelled. If there be a particle of clearance at the end of a piston stroke the quantity'of air contained in said clearance represents the quantity of air which can never be expelled nectionwith it and which constitutes the movable end or wall of the cylinder within which the first named piston actually moves, it being immaterial whether the piston contacts with a fixed or movable wall so long as it is firmly seated against such wall to thereby expel all air betweensaid piston and said wall.

I claim- 1. A vacuum pump containing the following inst-rumentalities, viz:a pump cylinder, an inlet and outlet therefor; a cut-off piston to open and close said inlet; a main piston; one or more passages therein through which fluid drawn into said cylinder is forced; and means to reciprocate said pistons, substantially as described.

2. A vacuum pump containing the following instrumentalities, viz:a pump cylinder, an air inlet therefor, a pump piston therein; a power cylinder, its piston connected with and to move said pump piston; valves to control the movements of said power piston and its connected pump piston; and independent automatic valve operating mechanism actu-' ated independently of said pistons whereby the movements of said valves may be varied at will irrespective of said pistons, substantially as described.

3. A vacuum pump containing the following instrumentalities, viz:a pump cylinder, an air inlet in the side thereof near one end; a tubular cut-off piston within said cylinder tocover and uncover said inlet; a main piston moving within said tubular piston; one or more passages in said main piston through which fluid drawn into said cylinderis forced; valves controlling said passages, and means to reciprocate said pistons to operate, substantially as described.

4;. A vacuum pump containing the following instrumentalities, viz:a pump cylinder; an air inlet in the side thereof; main and cutoff pistons in said cylinder; two power cylinders and pistons therein connected respectively with said main and cut-off pistons, substantially as described.

5. A vacuum pump containing the following instrumentalities,viz:a pump cylinder; an air inlet in the side thereof; main and cutofi pistons in said cylinder; two power cylinders arranged with axes coincident with the axis of said pump cylinder; and pistons therein connected respectively with said main and cut-0E pistons, substantially as described.

6. A vacuum pump containing the follow- I ing instrumentalities, viz:a pump cylinder; an air inlet in the side thereof; pump pistons in said cylinder; two power cylinders; pistons therein connected respectively with and to actuate said pump pistons; and valves for sa1d power cylinders connected to move together, but having differently arranged ports to the reby produce different movements of said pistons, substantially as described. 7. A vacuum pump containing the following iustrumentalit-ies, viz:a pump cylinder; an air inlet in the side thereof at or near one IO end; main and cut-oif pistons therein and means to reciprocate the same, the said outoff piston being moved to open and again close said port while the main piston is moving in one direction, substantially as de- 5 scribed.

8. A vacuum pump containing the following instrumentalities,viz:-a pump cylinder; an air inlet in the side thereof; main and cutoif pistons in said cylinder moving one within 2 the other, and at the ends of their reciprocations in one direction resting upon a common cylinder head, substantially as described.

9. A vacuum pump, containing the followin g instrumentalities, viz:a pump cylinder;

an air inlet in the side thereof; main and cutoff pistons in said cylinder, moving one within the other, said pistons at the ends of their reciprocations in one direction resting upon a common cylinder head and at or near the ends 3 of their reciprocations in the opposite direction contacting one with the other, and valves in said pistons, substantially as described.

' 10. A vacuum pump containing the following instrumentalities, viz:-a pump cylinder;

an air inlet in the side thereof; main and cutofi pistons in said cylinders moving one within the other, the inner or main piston at the end of its drawing-in movement contacting with the cut-0E piston in its cutting-off movement,

4 the main piston changing its direction of movement to and returning for a time in unison with the further cutting-01f movement of the said cut-off piston, substantially as described.

11. A vacuum pump containing the following instrumentalitics, viz:-a pump cylinder provided with valves; an air inlet for said cylinder; two pistons moving one within the other in said cylinder; valves in and means 5 to move said pistons whereby a vacuum is formed between the two pistons into which the air drawn into the cylinder is permitted to enter, anda second vacuum formed in the said cylinder between its end and said pistons into which the air from the space between said pistons is exhausted, substantially as described.

12. A vacuum pump containing the following instrumentalities, viz:a pump cylinder;

a cut-off piston therein cone shaped at its upper side, and having a cone-shaped recess at its under side; valves in said piston; a main piston movable within said cut-elf piston and also made crowning at its upper side and pro vided with a conical recess at its under side,

the conical cylinder head I) and head I) having a conical recess, valves in said main piston and in said cylinder head Z), power cylinders and pistons therein connected with and to move said main and cut-oil pistons, all to operate, substantially as described.

13. A vacuum pump containing the following instrumeutalities, viz:a pump cylinder; a pump piston therein; a power cyl1nder,a piston therein connected with and to operate said pump piston,a pressure creating device and power connections between it and the inlet and exhaust of said power-cylinder, whereby said device takes the exhaust flu d from said power-cylinder and returns it again thereto under pressure to actuate the piston therein; valves controlling said inlet and exhaust, and means to actuate said valves and said pump, substantially as described.

14:. A vacuum pump containing the following instrumentalities,viz:-a pump cylinder; pump pistons therein; power cylinders and pistons therein connected respectively with and to operate said pump pistons; rotatable toothed intermeshing valves to control movements of said power pistons, and means to retate said valves, substantially as described.

15. A vacuum pump containing the following instrumentalities, viz:-a pump cylinder; pump pistons therein; power cylinders, pistons therein connected with and to operate said pump pistons; valve seats 0 6 provided respectively with exhaust depressions 0", c and inlet ports for the said power cylinders; valves h and 71/, having inlet ports h, hfland exhaust depressions h, h", and means to retate said valves, all to operate, substantially as described.

16. A vacuum pump containing the following instrumentalities, viz:--a pump cylinder; pistons therein; power cylinders, pistons therein connected with and to operate said pump pistons; rotatable valves for and to control said power cylinders; and worm-wheel mechanism to rotate said valves, substantially as described.

17. A vacuum pump containing thefollowing instrumentalities, viz:-a pump cylinder, pistons therein; power cylinders, pistons therein connected with and to operate said pump pistons; valves to control said power cylinders and the movements of the pistons therein; a pressure creating device, as the pump I, to create pressure to actuate the power pistons; and common actuating mechanism for said valves and pressure creating device whereby the pressure created varies with and follows the movements of said valves, substantially as described.

18. A vacuum pump containing the following instrumentalities,vizz-a base; a plurality of pump cylinders, pistons in each; power cylinders and pistons therein connected with and to actuate the said pump pistons, valves for the said power pistons; common actuating mechanism for said Valves whereby the pistons in the said power cylinders are caused IIO to move uniformly with relation to each other; ciprocate said pistons relatively to each other, a single pressure creating deviceto supply substantially as described. fluid under pressure for and to operate said In testimony whereof I have signed my power pistons, substantially as described. name to this specification in the presence of 5 19. A vacuum pump containing the followtwo subscribing witnesses.

ing-instrumentalities, viz:a pump cylinder; EDWIN D. OHAPLINZ a main box-like piston f adapted to be filled Witnesses:

with oil, and a cut-off piston e, both in said HENRY G. HALLORAN, cylinder; valves f and e and means to re- FREDERICK L. EMERY. 

